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What ePWM registers set the module to active high?

William Friesen
Intellectual 990 points
Other Parts Discussed in Thread: CONTROLSUITE, DRV8312

What register/value tells the ePWM to be active high?  I am happy to "read the funny manual" if I can get pointed to the right manual.

According to the SPRUH18D (page 273) it appears that setting this 2 bit field (EPwm1Regs.AQCTLA.bit.CAU) to “AQ_CLEAR” makes the ePWM to be active high.  It also sets EPwm1Regs.AQCTLA.bit.ZRO to "AQ_SET".  Are both required in order to get the ePWM module to be active high.

Page 276 EPwm1Regs.AQCTLA.bit.PRD is set to AQ_CLEAR as part of setting the ePWM module to be active low.  What should it be to get active high?

In one of the example projects it sets the CAU to CLEAR and CAD to SET.  What is the role of CAD?

  • 0
    TI__Guru* 92780 points

    William Friesen said:
    it appears that setting this 2 bit field (EPwm1Regs.AQCTLA.bit.CAU) to “AQ_CLEAR” makes the ePWM to be active high.

    The "clear" action will set the ePWM output low.  A set action will set the output high.

    First start with the Counter Compare module.  The PWM counter is ticking away, lets say in up-down count mode.   In the Counter Compare module you specify two compare values: CMPA and CMPB.  

    Then in the Action Qualifier registers you specify the action to take when the counter is equal to that value.   In the case above this says "On the counter equal to CMPA on an upcount take this action on the EPWMA output".  In this case the action is "CLEAR" which means pull the output low. 

    William Friesen said:
    Page 276 EPwm1Regs.AQCTLA.bit.PRD is set to AQ_CLEAR as part of setting the ePWM module to be active low.  What should it be to get active high?

    Set and clear are not really tied to "an active high epwm" per sey.  They indicate what action the module should take at which compare value - pull the output to a high state or pull the output to a low state.  If you wanted to invert the drawing in the above screenshot then you would swap the set with clear and clear with set.

    William Friesen said:
    In one of the example projects it sets the CAU to CLEAR and CAD to SET.  What is the role of CAD?

    CAD is "TBCNTR equal to compare A and TBCNTR is counting down"  (instead of up). 

  • 0 in reply to Lori Heustess
    TI__Guru* 92780 points

    You may find the Piccolo multi-day workshop chapter on the ePWM helpful to get started.  

    http://processors.wiki.ti.com/index.php/C2000_Piccolo_Multi-Day_Workshop

    Module 7

    Cheers

    Lori

  • 0 in reply to Lori Heustess
    Intellectual 990 points

    Wow thanks so much.  I will review module 7 again, but I missed the explanation on the AQCTLx modules.   It would really be cool if TI would put the training videos onto the TI web site. . .Someone began to do this for the CCSv5. 

    I have all of the parts to test.  So I might work through the lab.

    I am still confused.  Perhaps I am over thinking this.  My goal will be to modify one of the ControlSUITE projects.  The High Voltage Development kit has a P over N inverter.  I need the BLDC project to run on an N over N inverter.  Unfortunately this build has not yet been ported to the DRV8312 platform.